1. Field of the Invention
The present invention relates to a non-contact transformer in which electrical current is transmitted between non-contacting first and second transformer components located in mutual opposition to each other.
2. Description of Background Information
Conventional transformer T, as shown in FIG. 6, includes a primary transformer component 3 installed within primary housing 2, and secondary transformer component 5 installed within secondary housing 4, the housings being oriented in mutual opposition to each other. Electromagnetic inductance, which occurs between primary coil 8 of primary transformer component 3 and secondary coil 9 of secondary transformer component 5, induces non-contact electrical current transmission between primary transformer component 3 and secondary transformer component 5. Due to its ability to provide non-contact electrical current transmission, non-contact transformer T can be provided for example, in an electrical appliance that is exposed to water such as an electric toothbrush or electric shaver shown as appliance X in FIG. 6, and into charging device Y which is used to electrically charge appliance X. The non-contact transformer allows charging device Y to safely supply electricity to the terminals on appliance X, even when appliance X is wet, without a physical connection being established between appliance X and charging device Y. With primary transformer component 3 installed within primary housing 2 to form charging unity Y, core space 1 is provided in secondary transformer component 5, instead of a solid ferrous core, in order to lower manufacturing costs, and the internal space of primary housing 2 is completely filled with resin 6 (FIG. 7) in order to improve heat dissipation and to waterproof the transformer. When resin 6 is poured into the internal space of primary housing 2, bottom plate 2a of primary housing 2 acts as the floor of the housing which is filled with resin 6. Because primary transformer component 3 is completely immersed within resin 6, core space 1 of primary transformer component 3 also becomes filled with resin 6.
It is desirable to bring primary transformer component 3 and secondary transformer component 5 into the closest mutual proximity to each other in order to obtain maximum electromagnetic inductance efficiency. To this end, the cylindrical end faces of primary housing 2 and secondary housing 4 (bottom plates 2a and 4a in this example) are brought into mutual contact. Terminals 12 are provided at the cylindrical end face of primary transformer component 3 opposite to bottom plate 2a of primary housing 2, and printed circuit board 7. As core space 1 is to be filled with resin 6, small gaps are provided between the respective cylindrical end faces of primary transformer component 3 where they meet bottom plate 2a of primary housing 2 and printed circuit board 7 in order to allow resin 6 to flow into core space 1. There is an inherent shortcoming, however, in that air core space 1 is a difficult space to fill with resin 6 because air present in core space 1 can become entrapped within resin 6 (residual air 15) with the inflow resin 6. The entrapment of residual air 15 within resin 6 can result in the distortion or breakage of primary housing 2 due to residual air 15 expanding from heat generated by the operation of primary transformer component 3.
Taking the above inherent problems into consideration, the present invention proposes a structure for non-contact transformer whereby the entrapment of residual air within the resin can be prevented and distortion and damage to the primary housing eliminated even though one side of the transformer core space is covered by the lower plate of the housing and the other side is covered by a printed circuit board.
The non-contact transformer of the present invention provides the following construction. A cylindrically shaped primary transformer component, which is installed within the primary housing, and cylindrically shaped secondary transformer component, which is installed with the secondary housing, are located in mutual opposition. An electromagnetic induction effect, occurring between the primary coil of the primary transformer component and the secondary coil of the secondary transformer component, induces non-contact electrical current transmission between the primary transformer component and the secondary transformer component. A cylindrical end face located on one side of the primary transformer component is attached to a bottom plate of primary housing which is located in opposition to the secondary housing. A printed circuit board, located on the other side of the primary transformer component, is provided on the cylindrical end face to which the terminals are attached. As the transformer component is enveloped within resin which fills the primary housing, a passage is provided between the printed circuit board and the primary transformer component. Even though bottom plate of the primary housing and the printed circuit board define a core space of the primary transformer component as a predominantly covered space, because the passage, which is located between the circuit board and the primary transformer component, provides a connecting space between the core space and the space external to the primary transformer component, the passage is able to guide the flow of resin into the core space while the air present in the core space exits to the space external to the core space at the time when the primary transformer becomes immersed within resin that fills primary housing. The result is that resin is able to flow into the core space of the primary transformer without entrapping residual air (FIG. 7).
The non-contact transformer of the present invention may include the provision of an external orifice which is located opposite to resin inflow point G within the primary housing and which opens to the space external to the primary transformer component at the end of the passage. As a result of this construction, resin will first flow around the external perimeter of the primary transformer component and then into the core space through the passage. That is, after first flowing into the space between the outer perimeter of the primary transformer component and the primary housing, a fairly steady volume of resin will flow smoothly through the passage to the core space. In other words, this structure is able to prevent the passage from becoming suddenly filled by a fast inflow of resin which would prevent air from escaping from the core space. A mechanism is thus formed which creates a more stable flow of resin into the core space to further reduce the chances of residual air from the core space becoming entrapped within resin.
The non-contact transformer of the present invention may include the provision of a resin passage, located between the bottom plate of the primary housing and the primary transformer component, that connects the core space of the primary transformer component to the space external to the primary transformer component. The resin passage is thus able to direct the flow of resin from within the primary housing into the core space to the external environment. The separate functions provided by the passages allow for the escape of air from the core space and for the smooth flow of resin into the core space and thus form a mechanism able to further reduce the possibility of trapping the air present in the core space as residual air within resin.
An aspect of the present invention provides a non-contact transformer including a primary cylindrical transformer component provided within a primary housing and a secondary cylindrical transformer component provided within a secondary housing located opposite the primary housing to induce non-contact electrical current transmission between the primary transformer component and the secondary transformer component through electromagnetic inductance occurring between a primary coil in the primary transformer component and a secondary coil in the secondary transformer component, the non-contact transformer including a cylindrical end face of the primary transformer component provided on a bottom plate of the primary housing located opposite the secondary housing; a printed circuit board with terminals attached thereto provided on another cylindrical end face of the primary transformer component; and a passage that receives resin as the primary transformer component is immersed in resin filling the primary housing, the passage provided between the printed circuit board and the primary transformer component and connecting a core space within the primary transformer component and a space external to the primary transformer component.
In a further aspect of the present invention, an external orifice may be provided on the perimeter of the primary transformer component at the passage, the external orifice located on the opposite side of the primary transformer component from where resin is poured into the primary housing. Further, a resin passage may be provided between the primary housing bottom plate and the primary transformer component and connecting a core space within the primary transformer component with a space external to the primary transformer component. An external orifice may further be provided on the perimeter of the primary transformer component at the passage, the external orifice located on the same side of the primary transformer component as where resin is poured into the primary housing. Further, the passage may run in a linear, radial path from the core space within the primary transformer component to the space external to the primary transformer component.
According to a further aspect of the present invention, the primary transformer component includes a coil channel therearound, the cylindrical end face of the primary transformer component provided on the printed circuit board and the coil channel are separated by a distance A, and the depth of the passage from the cylindrical end face of the primary transformer component is B, so that:
B less than A. 
According to a further aspect of the present invention, the resin passage provided between the primary housing bottom plate and the primary transformer component runs in a linear, radial path from the core space within the primary transformer component to the space external to the primary transformer component. Further, the primary transformer component may include a coil channel therearound, the cylindrical end face of the primary transformer component provided on the primary housing bottom plate and coil channel are separated by a distance C, and the depth of the resin passage from the cylindrical end face of the primary transformer component provided on the primary housing bottom plate is D, so that:
D less than C. 
Further, a first external orifice may be provided on the perimeter of the primary transformer component at the passage between the cylindrical end face of the primary transformer component and the printed circuit board, a second external orifice is provided on the perimeter of the primary transformer component at the resin passage between the primary transformer component and the primary housing bottom plate, and the first external orifice is located on the opposite side of the primary transformer component from the second external orifice.
A further aspect of the present invention provides a primary transformer component for a non-contact transformer, the primary transformer component attached to a bottom plate of a primary housing and including a primary coil, the primary transformer component including a cylindrical end face of the primary transformer component provided on the bottom plate of the primary housing; a printed circuit board with terminals attached thereto provided on another cylindrical end face of the primary transformer component; and a passage that receives resin as the primary transformer component is immersed in resin filling the primary housing, the passage provided between the printed circuit board and the primary transformer component and connecting a core space within the primary transformer component and a space external to the primary transformer component.
A further aspect of the present invention includes in combination, a rechargeable electric appliance; a non-contact transformer; and a primary transformer component.